r  rz  *  7 
630.7  ’ 
l  W27b  ’ b 
\  no i 69 
cop. 3  = 

WASHINGTON  STATE  AGRICULTURAL  COLLEGE 

and 

SCHOOL  OF  SCIENCE, 


EXPERIMENT  STATION, 

PULLMAN,  WASHINGTON. 


Bulletin  69 


Department  of  Botany  and  Zoology 


Preliminary  Report  on  the  Codling  Moth  in  the 
Yakima  Valley. 


By  Eldred  Jenne 


All  bulletins  o£  this  station  sent  free  to  citizens  of  the  state  on  application  to  the 

Director. 


ALLEN  BROS.,  PRINTERS,  TULLMAN. 


UNIVERSITY  OF 
ILLINOIS  LIBRARY 
AT  URBANA-CHAMPAIGN 

agriculture 


THE  AGRICULTURAL  EXPERIMENT  STATION. 


BOARD  OF  CONTROL: 

F.  J.  Barnard,  President  -  -  Seattle 

R.  C.  McCroskey . -  Garfield 

H.  D.  Crow . Spokane 

J.  P.  Sharp  * . Ellensburg 

U.  L.  Ettinger,  Treasurer . Colfax 

STATION  STAFF. 

Enoch  A.  Bryan,  A.  M.,  LL.D.,  . Director 

President  of  the  College. 

Elton  Fulmer,  M.  A.,--------  -  State  Chemist 

S.  B.  Nelson,  D.  V.  M., . Veterinarian 

E.  E.  Elliott,  M.  S., . Agriculturist 

O.  L.  Waller,  Ph.  M., . Irrigation  Engineer 

R.  W.  Thatcher,  M.  A., .  Chemist 

R.  K.  Beattie,  A.  M., . Acting  Botanist 

H.  S.  Davis,  Ph.  B., . Assistant  Zoologist 

George  Severance,  B.  S.,  -  -  -  -  Assistant  Agriculturist 

A.  L.  Melander,  M.  S. . Assistant  Entomologist 

Maynard  Rosenberger,  D.V.M.  -  -  Assistant  Veterinarian 

W.  H.  Lawrence,  M.  S. . Assistant  Botanist 


*  Deceased,  February  9th,  1905. 


. 


' 

■ 


* 

* 


Preliminary  Report  on  the  Codling  Moth  in  the 
Yakima  Valley* 


BY  EEDRED  JENNE. 


Introduction: — The  following  notes  are  taken  from  the  writ¬ 
er’s  report  on  the  work  done  on  the  Codling  Moth  during  the 
summer  of  1903,  in  the  vicinity  of  North  Yakima  and  Zillah.  The 
work  was  carried  on  by  the  State  Experiment  Station  at  Pullman, 
and  was  particularly  outlined  and  directed  by  Prof.  C.  V.  Piper, 
then  of  the  Station  staff. 

The  plan  of  the  work  was  to  follow  closely,  in  the  orchard  and 
in  breeding  cages,  the  life  history  and  habits  of  the  Codling  Moth 
during  the  season,  and  also  to  gather  data  regarding  the  means  at 
present  in  use  for  combating  the  pest.  In  short,  the  object  was  to 
study  existing  conditions  in  regard  to  the  Codling  Moth  in  the  Ya¬ 
kima  valley,  with  the  end  in  view  of  later  carrying  out  spraying 
experiments  based  upon  these  observations.  The  work  will  prob¬ 
ably  be  continued  during  the  next  season,  after  which  the  inten¬ 
tion  is  to  to  publish  in  full  the  results  of  both  years’  work.  Mean¬ 
while  a  few  of  the  results  of  the  work  of  1903  which  may  be  of  use 
to  orchardists  in  combating  the  Moth  during  the  coming  season 
are  published  herewith. 


Life  History  of  the  Codling  Moth. 

The  plan  followed  in  studying  the  life  history  of  the  Codling 
Moth  was  to  follow  its  development  in  one  particular  orchard  as 
closely  as  possible,  this  work  being  checked  by  observations  made 
from  time  to  time  in  as  many  other  orchards  as  possible.  The 
orchard  of  Mr.  W.  L.  Wright,  near  North  Yakima,  was  selected 
as  headquarters,  and  here  all  the  breeding  cage  work  was  done, 
this  forming  the  basis  of  the  life  history  studies.  The  results  ob- 


6 


Washington  Agricultural  Experiment  Station 


tained  from  the  breeding  cage  work  were  checked  by  constant 
observations  in  the  orchard. 

A  summary  of  the  data  obtained  on  the  life  history  of  the  Cod¬ 
ling  Moth  is  shown  graphically  in  the  accompanying  diagram. 


Number  of  Broods* 

One  of  the  principal  aims  of  the  life  history  studies  was  to  de¬ 
termine  the  number  of  generations  or  “broods”  which  the  insect 
produces  in  a  season,  as  this  has  been  a  much  disputed  point  with 
observers.  The  results  are  given  briefly  below. 

At  least  two  generations  or  “broods”  undoubtedly  occur,  as 
represented  in  the  accompanying  diagram,  separated  by  a  period 
of  about  twenty  days.  The  gap  was  observed  in  the  orchard  be¬ 
tween  the  two  broods  of  eggs,  between  the  times  when  freshly 
stung  apples  were  found,  and  in  the  record  of  worms  caught  from 
banded  trees.  The  two  generations  were  also  bred  in  cages.  Part 
of  the  band  record  is  given  below. 

Part  of  daily  record  of  worms  caught  from  24  banded  trees  in 
the  orchard  of  W.  L.  Wright,  showing  gap  between  the  first  two 
broods: 


DATE 

NO.  WORMS 

DATE 

NO.  WORMS 

DATE 

NO.  WORMS 

July  17. 

. l6 

July  26. 

. 4 

Aug.  4. 

<  i 

18. 

“  27. 

. 5 

“  5- 

i  i 

19. 

. 18 

“  28. 

. 0 

“  6. 

. 2 

<  < 

20. 

“  29 

“  7- 

. 2 

<  < 

21 . 

. 8 

“  30. 

. 2 

“  8. 

. 6 

cc 

22. 

. 9 

“  3i- 

.  2 

“  9- 

. 6 

<  < 

23- 

. 7 

Aug.  1 . 

.  3 

“  10. 

. 12 

i  ( 

24. 

. 4 

“  2. 

“  11. 

. 13 

( < 

23- 

. 4 

“  3 

. O 

“  12. 

As  shown  here  the  gap  between  the  first  two  broods  at  the 
time  of  the  worms  leaving  the  apples  occurs  between  July  20  and 
August  10,  (1903),  indicated  by  the  few  worms  appearing  under 
the  bands  between  these  dates.  The  same  gap  is  shown  graphic¬ 
ally  in  the  curve  below. 


Bulletin  No.  69 — Preliminary  Report  on  the  Codling  Moth  7 


Curve  representing  the  band  record  for  the  season.  The  height 
of  the  curve  above  the  base  line  represents  the  number  of  larvae 
caught  at  any  one  time. 

Late  Pupae.  (Third  Generation.) 

As  soon  as  the  sudden  decrease  (July  20)  in  the  number  of 
worms  appearing  under  the  bands  was  noticed,  all  the  worms 
caught  each  day  were  kept  in  cages  so  as  to  determine  the  per 
cent,  which  would  pupate  and  the  per  cent,  to  pass  the  winter  as, 
larvae. 

The  results  are  given  in  the  following  table  : 

Wn^iTnTd  No.  Pupating  No.  Wintering 


July  24-27 .  12.. 

“  27 .  5.. 

Aug.  2 .  3., 

“  4 .  5- 

“  5 .  3- 

“  6 .  9- 

“  9 .  5- 

“  10 .  14.. 

“  11 .  12.. 

“  12 .  7.. 

“  13  .  10  • 

“  i5 .  3- 

“  17  9- 

“  18 .  12.. 

“  20 .  12.. 

“  21  4.. 


o 

1 

1 

1 

o 

I 

o 

5 

6 

3 

1 

2 

3 
8 

9 

5 


23 . 

.  2 . 

.  22 

26 . 

..  2 . 

......  19 

28 . 

..  0 . 

.  19 

29 . 

..  0 . 

i-Aug. 

21 .. 

•103 . 

.  59 

I-  “ 

28.. 

•  85 . 

. 115 

21-Sept. 

3-** 

.  20 . 

. 207 

28-  “ 

3** 

.  0 . 

.  5i 

8 


Washington  Agricultural  Experiment  Station 


From  the  above  table  it  will  be  seen  that  the  first  larva  des¬ 
tined  to  pass  the  winter  as  such  appeared  under  the  band  on  July 
27.  No  more  were  caught  which  did  not  pupate  until  Aug.  2,  but 
from  then  on  until  Aug.  20  the  proportion  which  did  not  pupate 
gradually  increased.  It  should  be  noticed,  however,  that  the  ac¬ 
tual  number  of  those  which  pupated  also  increased  and  up  till  Aug. 
21  exceeded  those  which  did  not  pupate.  But  about  Aug.  21  pu¬ 
pation  declined  abruptly  and  after  another  week  all  the  worms 
which  left  the  apples  went  into  winter  quarters,  the  last  worm  to 
pupate  appearing  under  the  band  Aug.  26.  It  should  be  noticed 
that  the  dates  given  in  the  table  above  are  those  on  which  the 
worms  appeared  under  the  bands,  the  dates  of  pupation  for  those 
which  did  pupate  being  a  week  or  ten  days  later  at  this  season  of 
the  year.  The  last  pupa  appeared  Sept.  4  from  a  worm  which 
appeared  under  the  band  on  Aug.  26.  At  Zillah,  Mr.  F.  Walden 
removed  the  bands  from  his  orchard  of  3000  trees  on  Aug.  24  and 
again  on  Sept.  5.  A  rough  count  was  kept  of  the  number  of  pu¬ 
pae  caught  when  the  bands  were  removed  the  last  time,  and  it  was 
estimated  that  500  pupae  were  taken  from  the  3000  trees.  No 
pupae  appeared  in  this  orchard  after  Sept.  5.  In  general  it  may 
be  said  that  for  a  season  like  the  one  of  1903  pupation  practically 
ceases  by  Sept.  1st.  This  date  is  important  to  those  who  use  bands 
for  trapping  the  worms,  because  after  pupation  has  ceased  it  is  not 
necessary  to  remove  the  bands  again  until  the  crop  is  harvested. 

Evidence  of  a  Third  Brood. 

Since  the  Codling  Moth  always  passes  the  winter  as  a  larva  it 
is  evident  that  if  some  of  the  second  generation  of  larvae  could  be 
proved  to  pupate,  it  would  be  beyond  a  doubt  that  at  least  some 
of  the  insects  pass  through  three  generations.  Now  from  the  band 
record  it  will  be  seen  that  most  of  the  first  brood  of  worms  had 
left  the  apples  by  July  1,  and  as  during  this  time  of  the  year  the 
worms  do  not  remain  in  the  apples  much  over  twenty  days,  all  of 
the  first  brood  of  worms  should  have  left  the  apples  at  least  by 
Aug.  1.  It  therefore  seems  certain  that  those  worms  which  left 
the  apples  and  pupated  after  Aug.  1  and  as  late  as  Aug.  26  must 
have  been  of  the  second  generation,  the  resulting  moths  being  a 
third  generation  of  moths. 


Bulletin  No.  69 — Preliminary  Report  on  the  Codling  Moth  9 


Again  it  will  be  seen  from  the  table  given  above  that  the  actual 
number  of  worms  which  pupated  increased  from  Aug.  1  to  Aug. 
21,  whereas  if  only  larvae  of  the  first  brood  pupated  the  number 
should  have  steadily  decreased  during  this  time,  not  only  in  pro¬ 
portion  to  the  number  which  did  not  pupate,  but  also  absolutely. 

Another  reason  for  believing  that  these  late  pupae  belong  to  a 
third  generation  is  that  both  band  record  and  orchard  observa¬ 
tions  show  a  distinct  gap  of  about  twenty  days  between  the  two 
broods,  while  if  the  late  pupae  are  taken  as  belonging  to  the  sec¬ 
ond  brood  of  pupae  it  would  indicate  an  overlap  of  more  than 
twenty  days  between  the  broods;  an  overlap  from  the  time  the 
first  wintering  larva  appeared,  July  27,  to  the  time  when  the  last 
worm  appeared  under  the  band  to  pupate,  Aug.  26. 

It  will  be  noticed  from  the  table  given  above  that  pupation  de¬ 
clined  abruptly  about  Aug.  20.  Now  a  temperature  record  was 
kept  during  the  summer  and  it  shows  that  after  Aug.  22  the  tem¬ 
perature  was  decidedly  lower  than  before.  From  Aug.  10  to  20 
the  average  temperature  from  7  to  9  p.  m.  was  about  73  degrees, 
while  from  Aug.  20  to  30  it  was  65  degrees.  This  dropping  of 
the  temperature  at  about  the  time  when  pupation  ceased  suggests 
the  idea  that  it  may  depend  much  upon  the  temperature  at  the 
time  whether  or  not  a  worm  will  pupate  or  live  over  winter.  In 
1903  not  more  than  a  very  small  proportion  of  the  worms  of  the 
second  brood  pupated,  but  it  would  be  expected  that  this  propor¬ 
tion  would  vary  in  different  years  according  to  the  fall  temper¬ 
ature  and  might  in  a  favorable  season  become  of  considerable  im¬ 
portance,  perhaps  so  much  so  as  to  make  necessary  an  extra 
spraying  during  September. 


IO 


Washington  Agricultural  Experiment  Station 


Codling  Moth  Calendar — Showing  graphically  the  life  history  of  the 
Codling  Moth  as  observed  during Ithe  summer  of  1903. 


Bulletin  No.  69 — Preliminary  Report  on  the  Codling  Moth  1 1 


Relation  of  Life  History  to  Spraying; 

It  is  evident  that  to  get  the  greatest  possible  benefit  from  spray¬ 
ing,  it  should  be  done  just  before  the  worms  enter  the  apples,  ex¬ 
cept  possibly  in  the  case  of  the  first  spraying  of  the  season,  which 
many  prefer  to  give  immediately  after  the  blossoms  have  fallen  so 
that  some  of  the  poison  will  be  inclosed  within  the  calyx  lobes 
when  they  close.  In  orchards  where  from  seven  to  ten  sprayings 
are  used  there  is  no  doubt  that  some  of  them  could  be  profitably 
left  out;  but  the  trouble  comes  in  deciding  which  ones  to  leave  out. 
This,  of  course,  depends  upon  the  time  when  the  young  worms  en¬ 
ter  the  apples.  It  has  commonly  been  supposed  among  orchard- 
ists  that  from  the  time  when  the  first  worms  enter  in  the  spring 
until  late  in  the  fall,  there  is  an  unbroken  procession  of  young 
worms  going  into  the  apples.  This  is  true  to  some  extent,  but 
this  work  and  also  the  observations  of  several  orchardists  have 
shown  that  at  one  place  there  is  an  almost  complete  break  of  about 
twenty  days  in  the  procession,  and  that  there  are  other  fluctua¬ 
tions.  In  other  words  the  great  majority  of  the  worms  enter  the 
apples  at  more  or  less  definite  times.  Thus  in  1903,  as  shown  in 
the  diagram,  the  first  brood  of  larvae  entered  during  the  month  of 
June.  Then  a  break  occurred  from  the  last  of  June  to  about  July 
20;  then  between  July  20  and  the  last  of  August  the  greater  part  of 
the  second  brood  of  worms  entered  the  apples.  From  the  last  of 
August  till  the  first  of  October  there  was  a  gradually  diminishing 
line  of  stragglers  entering  the  apples.  These  stragglers  may  be 
accounted  for  partly  as  members  of  a  partial  third  brood  and  partly 
as  late  members  of  the  second  brood  delayed  by  the  lower  temper¬ 
ature  of  the  fall.  The  time  during  which  the  worms  entered  the 
apples  during  1903  is  shown  by  the  following  diagram.  A  rough 
idea  of  the  comparative  numbers  entering  at  any  one  time  is  given 
by  the  height  of  the  curve  above  the  base  line. 


12 


Washington  Agricultural  Experiment  Station 


If  the  time  shown  in  the  above  diagram  were  the  same  for  all 
years,  the  problem  of  spraying  at  the  right  time  would  apparently 
be  a  simple  one;  but  the  difficulty  comes  in  determining  the  varia¬ 
tion  for  different  seasons.  Now,  the  time  when  the  first  worms 
will  enter  the  apples  may  always  be  reckoned  from  the  date  of 
blooming  of  the  apple  trees,  the  first  worms  entering  in  three 
weeks  or  a  little  less  after  the  blossoms  fall.  Then  if  the  orchard 
was  sprayed  while  the  calyx  cups  were  open,  the  second  spray¬ 
ing  should  be  about  two  weeks  later  in  order  to  catch  the  first 
worms.  These  two  sprayings  should  suffice  for  the  first  brood, 
and  if  fewer  than  the  five  sprayings  indicated  on  the  diagram  were 
to  be  given  during  the  year  it  is  likely  that  one  of  these  sprayings 
could  best  be  left  out,  especially  if  the  crop  is  heavy,  as  apples 
stung  by  the  first  brood  almost  always  fall  off  while  small,  and 
thus  a  natural  thinning  takes  place.  As  for  the  second  brood  it 
seems  that  three  sprayings  applied  at  the  times  indicated  on  the 
diagram  should  be  sufficient.  (It  should  be  remembered  that  these 
suggestions  as  to  the  time  of  sprayuig  are  based  solely  upon  the  life 
history  of  the  Codling  Moth  as  determined  during  the  season  of  1903, 
and  not  upon  actual  sy raying  experiments ,  as  no?ie  have  yet  been  un¬ 
dertaken.) 

In  deciding  when  to  spray  for  the  second  brood,  the  date  of 
blooming  of  apples  would  be  of  no  help  as  the  season  is  by  this 
time  so  far  advanced  that  weather  conditions  meanwhile  might 
considerably  change  the  date  of  appearance  of  the  second  brood. 
So  in  this  case  orchardists  must  for  the  present  depend  upon  their 
their  own  observation  and  judgment.  It  is  on  account  of  this  un¬ 
certainty  that  many  orchardists  prefer  to  spray  at  regular  intervals 
throughout  the  season  rather  than  take  the  chances  of  leaving  out 
a  spraying  at  the  wrong  time. 

Methods  of  Sptaying  Now  in  Use. 

It  is  supposed  by  some  orchardists  that  Paris  Green  spray  los¬ 
es  its  insectididal  properties  in  from  io  to  14  days  after  being  ap¬ 
plied,  and  that  it  therefore  needs  to  be  renewed  that  often.  The 
fact  is  that  Paris  Green  is  a  stable  chemical  compound  and  would 
keep  indefinitely  as  far  as  chemical  change  is  concerned.  The  only 
things  which  make  renewal  of  the  spray  necessary  are:  first,  the 


Bulletin  No.  69 — Preliminary  Report  on  the  Codling  Moth  13 


removal  of  the  spray  by  mechanical  means,  such  as  rain;  and 
second,  the  thinning  out  of  the  coat  of  spray  on  the  apples,  caused 
by  the  growth  of  the  apples.  As  rain  is  almost  entirely  lacking  in 
the  Yakima  valley,  about  the  only  way  in  which  the  spray  is  re¬ 
moved  is  by  the  rubbing  together  of  leaves  or  apples,  caused  by 
wind.  If  plenty  of  lime  is  used  in  the  spray,  it  is  not  hard  to  tell 
when  it  needs  renewal.  The  number  of  sprayings  used  by  differ¬ 
ent  orchardists  varies  greatly  according  to  the  different  opinions 
held  by  each.  Some  spray  at  regular  intervals  of  from  two  to  four 
weeks,  giving  in  all  six  to  ten  sprayings  during  the  year.  Others 
spray  irregularly  at  such  times  as  they  think  necessary.  Most  of 
the  latter  class  use  only  three  to  six  sprayings  during  the  year. 
Some  spray  while  the  calyx  cup  is  open,  while  others  think  this 
spraying  unnecessary,  although  it  is  undoubtedly  effective.  Com¬ 
plete  data  in  regard  to  the  treatment  for  the  Codling  Moth  and 
the  results  of  each  were  collected  in  twelve  of  the  largest  orchards 
of  the  valley,  but  the  space  is  not  sufficient  to  give  them  here. 

Spraying  Machinery. 

A  notion  prevails  among  a  few  more  or  less  inexperienced  or¬ 
chardists  that  when  Paris  Green  is  once  thoroughly  “dissolved,” 
the  spray  is  poisoned  and  that  no  further  attention  is  necessary. 
The  fact  is  that  Paris  Green  is  insoluble  in  water  and  cannot  be 
dissolved  as  sugar  or  salt  will  dissolve,  but  is  simply  held  in  sus¬ 
pension,  like  dust  in  water,  and  being  heavy,  will  quickly  settle  to 
the  bottom  if  the  spray  is  not  kept  constantly  stirred.  Hence  the 
importance  of  having  a  good  agitator  in  the  spraying  machine. 
If  the  agitator  is  not  effective  the  trees  will  be  sprayed  with  prac¬ 
tically  nothing  but  water  and  the  hose  and  nozzles  will  constantly 
become  clogged  and  after  each  barrelful  of  spray  is  used,  a  greater 
or  less  portion  of  the  Paris  Green  will  be  found  as  a  residue  in  the 
bottom  of  the  barrel.  With  a  good  agitator  it  should  only  occas¬ 
ionally  be  necessary  to  clean  out  the  machine,  and  then  only 
lumps  of  lime  etc.  should  be  found.  Next  after  the  agitator  the 
most  important  thing  is  to  get  as  great  pressure  as  possible. 

Two  main  types  of  nozzles  are  in  general  use:  those  which 
throw  a  fan-shaped  spray  (Bordeaux  and  San  Jose),  and  those 
which  give  a  cone-shaped  spray  (Vermorel.)  The  Vermorel  type 


14 


Washington  Agricultural  Experiment  Station 


gives  the  finest  spray  and  is  most  often  used  with  hand  pumps, 
although  many  prefer  the  Bordeaux.  In  the  case  of  power  spray¬ 
ing  machines,  which  on  account  of  the  greater  pressure  produces 
a  finer  spray  than  hand  pumps,  the  Bnrdeaux  nozzles  are  more 
used. 

Most  of  the  orchards  in  the  Yakima  valley  are  too  small  to 
warrant  the  purchase  of  expensive  power  spraying  outfits.  A  few 
are  in  use,  however,  and  have  proved  profitable.  Their  chief  ad¬ 
vantage  is  in  the  greater  pressure  which  they  furnish  and  in  their 
greater  capacity,  requiring  fewer  refillings.  A  power  sprayer  is 
effective  in  a  wind  that  would  stop  any  hand  pump,  and  the  finer 
spray  which  they  give  on  account  of  the  great  pressure  produces 
a  more  even  coating  over  the  trees  and  the  spray  does  not  have  so 
great  a  tendency  to  collect  into  large  drops  and  fall  off. 

Sprays. 

Paris  green  is  practically  the  only  insecticide  used  against  the 
Codling  Moth  in  the  Yakima  valley.  It  is  the  intention  of  some 
of  the  orchardists  to  test  other  arsenites  and  spraying  compounds 
in  the  future.  The  amount  of  paris  green  used  to  ioo  gallons  of 
water  varies  with  different  orchardists  from  three-fourths  of  a 
pound  to  one  and  one-half  pounds  and  the  amount  of  lime  from 
four  to  sixteen  pounds,  the  usual  amount  being  from  four  to  ten 
pounds.  Where  a  large  amount  of  lime  is  used  the  object  usually 
is  to  make  the  spray  show  up  well  when  dry,  so  as  to  be  able  to 
tell  when  it  needs  renewal.  The  main  purpose  of  the  lime  is  to 
prevent  burning  of  the  trees  by  the  free  arsenic  in  the  paris  green. 
To  do  this  it  is  necessary  to  use  only  a  few  ounces  of  lime  to  a 
pound  of  paris  green,  the  extra  lime  being  for  the  purpose  of  mak¬ 
ing  the  spray  more  conspicuous.  It  may  be  that  an  excessive 
amount  of  lime  would  impair  the  action  of  the  paris  green. 

Banding. 

The  practice  of  banding  the  trees  in  order  to  catch  the  worms 
which  cocoon  under  them  has  been  pretty  generally  abandoned 
throughout  the  Yakima  valley,  although  a  few  orchardists  still 
use  the  bands.  In  the  orchard  of  Mr.  F.  Walden,  near  Zillah, 
where  the  banding  system  is  still  used,  the  cost  of  removing  the 


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